Multilayered articles and method of manufacture thereof

ABSTRACT

Disclosed herein is a multilayered sheet comprising a core layer comprising a thermoplastic polymer and an IR absorbing additive; a first cap layer comprising a thermoplastic polymer and an electromagnetic radiation absorbing additive; wherein a surface of the first cap layer is disposed upon and in intimate contact with a surface of the core layer. Disclosed herein too is a method for manufacturing a multilayered sheet comprising melt blending a composition comprising a thermoplastic polymer and an IR absorbing additive to produce a core layer; melt blending a composition comprising a thermoplastic polymer and an ultraviolet radiation absorber to produce a first cap layer; combining the core layer with the first cap layer in such a manner that the cap layer is disposed upon and in intimate contact with a surface of the core layer.

BACKGROUND

This disclosure relates to multilayered articles and methods ofmanufacture. In particular this disclosure relates to multilayeredsheets for absorption of IR radiation and methods of manufacturethereof.

Absorption of excessive amounts of solar radiation by the interiorsurfaces of a vehicle, residential home or office building can result inelevated interior temperatures, reduced comfort for the occupants,accelerated degradation of interior materials, and an increase in therequirement for larger air conditioning units. In vehicles especially,under high static-soak conditions, which can occur in vehicles parked inthe hot summer sun, especially in a desert climate, surface temperaturewithin a closed car can reach over 100° C., and the entire thermal massof the car can be raised to high temperatures.

Increasing the cooling load of the air conditioning unit in a vehicle toameliorate heat discomfort would go against the trend currentlyprevailing in the automobile industry. Automobile engines are beingdownsized to reduce weight and improve fuel efficiency and are less ableto handle the power drain of the larger air conditioners. A recentconcern to industry and Government is the role played by automotive airconditioners as a source of chlorofluorocarbons (CFC) released into theatmosphere, increased cooling load will lead to even larger airconditioning units, which will exacerbate this problem. Thus, there is aneed for new technologies and passive design solutions, which would leadto reduced solar heat loads in automobiles as well as for residentialand office buildings.

SUMMARY

Disclosed herein is a multilayered sheet comprising a core layercomprising a thermoplastic polymer and an IR absorbing additive; a firstcap layer comprising a thermoplastic polymer and an electromagneticradiation absorbing additive; wherein a surface of the first cap layeris disposed upon and in intimate contact with a surface of the corelayer.

Disclosed herein too is a method for manufacturing a multilayered sheetcomprising melt blending a composition comprising a thermoplasticpolymer and an IR absorbing additive to produce a core layer; meltblending a composition comprising a thermoplastic polymer and anultraviolet radiation absorber to produce a first cap layer; combiningthe core layer with the first cap layer in such a manner that the caplayer is disposed upon and in intimate contact with a surface of thecore layer.

Disclosed herein is a method for manufacturing a multilayered sheetcomprising co-extruding a core layer comprising a thermoplastic polymerand an IR absorbing additive with a first cap layer comprising athermoplastic polymer and an ultraviolet radiation absorber.

Disclosed herein too are articles comprising the multilayered sheetdetailed above.

DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic depicting a core layer disposed between two caplayers in accordance with the invention;

FIG. 2 is a schematic depicting a core layer disposed upon and inintimate contact with a single cap layer;

FIG. 3 is a schematic depiction of a multiwall sheet wherein therespective sheets are separated by brackets and having air pockets inbetween the brackets;

FIG. 4 are photographs of an object taken through two multilayer sheets,one multilayer sheet contained LaB₆ in the core layer, while the otherhad LaB₆ in the cap layer; and

FIG. 5 shows a device over which thermoforming experiments wereperformed.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Disclosed herein is a multilayered sheet that displays high absorptionof light in the ultra-violet (UV) region of the electromagneticspectrum, high absorption and high reflectance of light in the nearinfrared (IR) region, while providing high transmittance and lowreflectance for light in the visible region. The multilayered sheetcomprises a core layer comprising a thermoplastic polymer and an IRabsorbing additive. In one embodiment, a surface of the core layer isdisposed on and in intimate contact with a surface of a first cap layercomprising a thermoplastic polymer and an electromagnetic radiationabsorbing additive. In another embodiment, a surface of the core layeris disposed between and in intimate contact with a surface of a firstand a second cap layer, each of which comprises a thermoplastic polymerand an electromagnetic radiation absorbing additive. The multilayeredsheet is generally mounted in any application (e.g., a building orautomobile) in such a manner so that solar radiation impinges upon thecap layer prior to impinging upon the core layer. The multilayered sheetis preferably manufactured by co-extrusion, and this will be detailedlater. It is to be noted that all ranges disclosed herein are inclusiveand combinable.

The electromagnetic radiation absorbing additive may be an absorber ofany radiation from the electromagnetic spectrum. In an exemplaryembodiment, the electromagnetic radiation absorbing additive is anultraviolet (UV) radiation absorber. In another exemplary embodiment,the electromagnetic radiation absorbing additive is an IR absorbingadditive that can absorb IR radiation. In yet another exemplaryembodiment, the electromagnetic radiation absorbing additive is anadditive that can absorb IR radiation and UV radiation.

FIG. 1 is a schematic depicting a surface of a core layer disposed inbetween the surface of a first and the surface of a second cap layer,while FIG. 2 is a schematic depicting a surface of a core layer disposedupon and in intimate contact with a surface of only the first cap layer.Both the core and the cap layers may be a single sheet of athermoplastic polymer or multiple sheets of a thermoplastic polymer.From the FIGS. 1 and 2, it may be seen that the thickness of themultilayer sheet refers to the thickness of the core layer added to thethickness of the cap layer.

As stated above, both, the core and the cap layer comprise thermoplasticresins. Thermoplastic polymers that may be used are oligomers, polymers,ionomers, dendrimers, copolymers such as block copolymers, graftcopolymers, star block copolymers, random copolymers, and the like, aswell as combinations comprising at least one of the foregoing polymers.Suitable examples of thermoplastic polymers that can be used as the coreand cap layer are polyacetals, polyacrylics, polycarbonatespolystyrenes, polyesters, polyamides, polyamideimides, polyarylates,polyarylsulfones, polyethersulfones, polyphenylene sulfides, polyvinylchlorides, polysulfones, polyimides, polyetherimides,polytetrafluoroethylenes, polyetherketones, polyether etherketones,polyether ketone ketones, polybenzoxazoles, polyoxadiazoles,polybenzothiazinophenothiazines, polybenzothiazoles,polypyrazinoquinoxalines, polypyromellitimides, polyquinoxalines,polybenzimidazoles, polyoxindoles, polyoxoisoindolines,polydioxoisoindolines, polytriazines, polypyridazines, polypiperazines,polypyridines, polypiperidines, polytriazoles, polypyrazoles,polypyrrolidines, polycarboranes, polyoxabicyclononanes,polydibenzofuirans, polyphthalides, polyacetals, polyanhydrides,polyvinyl ethers, polyvinyl thioethers, polyvinyl alcohols, polyvinylketones, polyvinyl halides, polyvinyl nitriles, polyvinyl esters,polysulfonates, polysulfides, polythioesters, polysulfones,polysulfonamides, polyureas, polyphosphazenes, polysilazanes, or thelike, or combinations comprising at least one of the foregoingthermoplastic polymers. The preferred thermoplastic polymers for use inthe core layer are polycarbonates or copolymers of polycarbonate andpolysiloxane. The preferred thermoplastic polymers for use in the caplayer are polycarbonate, copolyestercarbonates, or blends of polyesterswith polycarbonates.

As stated above, the core layer may be a single sheet of a thermoplasticpolymer or multiple sheets of a thermoplastic polymer. It is preferredfor the thermoplastic polymer to be transparent to light in the opticalwavelength region of the electromagnetic spectrum. The core layergenerally comprises a polycarbonate and an IR absorbing additive. Asused herein, the terms “polycarbonate”, “polycarbonate composition”, and“composition comprising aromatic carbonate chain units” includescompositions having structural units of the formula (I):

in which greater than or equal to about 60 percent of the total numberof R¹ groups are aromatic organic radicals and the balance thereof arealiphatic, alicyclic, or aromatic radicals. Preferably, R¹ is anaromatic organic radical and, more preferably, a radical of the formula(II):-A¹-Y¹-A²-   (II)wherein each of A¹ and A² is a monocyclic divalent aryl radical and Y¹is a bridging radical having zero, one, or two atoms which separate A¹from A². In an exemplary embodiment, one atom separates A¹ from A².Illustrative examples of the Y¹ radicals are —O—, —S—, —S(O)—, —S(O)₂—,—C(O)—, methylene, cyclohexyl-methylene, 2-[2,2,1]-bicycloheptylidene,ethylidene, isopropylidene, neopentylidene, cyclohexylidene,cyclopentadecylidene, cyclododecylidene, adamantylidene, or the like. Inanother embodiment, zero atoms separate A¹ from A², with an illustrativeexample being biphenyl. The bridging radical Y¹ can be a saturatedhydrocarbon group such as methylene, cyclohexylidene or isopropylidene.

Polycarbonates may be produced by the Schotten-Bauman interfacialreaction of the carbonate precursor with dihydroxy compounds. Typically,an aqueous base such as sodium hydroxide, potassium hydroxide, calciumhydroxide, or the like, is mixed with an organic, water immisciblesolvent such as benzene, toluene, carbon disulfide, or dichloromethane,which contains the dihydroxy compound. A phase transfer agent isgenerally used to facilitate the reaction. Molecular weight regulatorsmay be added either singly or in admixture to the reactant mixture.Branching agents, described forthwith may also be added singly or inadmixture.

Polycarbonates can be produced by the interfacial reaction of dihydroxycompounds in which only one atom separates A¹ and A². As used herein,the term “dihydroxy compound” includes, for example, bisphenol compoundshaving general formula (III) as follows:

wherein R^(a) and R^(b) each independently represent hydrogen, a halogenatom, preferably bromine, or a monovalent hydrocarbon group, p and q areeach independently integers from 0 to 4, and X^(a) represents one of thegroups of formula (IV):

wherein R^(c) and R^(d) each independently represent a hydrogen atom ora monovalent linear or cyclic hydrocarbon group, and R^(e) is a divalenthydrocarbon group, oxygen, or sulfur.

Examples of the types of bisphenol compounds that may be represented byformula (III) include the bis(hydroxyaryl)alkane series such as,1,1-bis(4-hydroxyphenyl)methane, 1,1-bis(hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)propane (or bisphenol-A),2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)propane, 1,1 -bis(4-hydroxyphenyl)n-butane,bis(4-hydroxyphenyl)phenylmethane,2,2-bis(4-hydroxy-1-methylphenyl)propane,1,1-bis(4-hydroxy-t-butylphenyl)propane,2,2-bis(4-hydroxy-3-bromophenyl)propane, or the like;bis(hydroxyaryl)cycloalkane series such as,1,1-bis(4-hydroxyphenyl)cyclopentane,1,1-bis(4-hydroxyphenyl)cyclohexane, or the like, or combinationscomprising at least one of the foregoing bisphenol compounds.

Other bisphenol compounds that may be represented by formula (III)include those where X is —O—, —S—, —SO— or —S(O)₂—. Some examples ofsuch bisphenol compounds are bis(hydroxyaryl)ethers such as4,4-dihydroxydiphenylether, 4,4-dihydroxy-3,3′-dimethylphenylether, orthe like; bis(hydroxy diaryl)sulfides, such as4,4′-dihydroxydiphenylsulfide,4,4′-dihydroxy-3,3′-dimethyldiphenylsulfide, or the like; bis(hydroxydiaryl)sulfoxides, such as, 4,4′-dihydroxydiphenylsulfoxides,4,4′-dihydroxy-3,3′-dimethyldiphenylsulfoxides, or the like; bis(hydroxydiaryl)sulfones, such as 4,4′-dihydroxydiphenylsulfone,4,4′-dihydroxy-3,3′-dimethyldiphenylsulfone, or the like; orcombinations comprising at least one of the foregoing bisphenolcompounds.

Other bisphenol compounds that may be utilized in the polycondensationof polycarbonate are represented by the formula (V)

wherein, R^(f), is a halogen atom of a hydrocarbon group having 1 to 10carbon atoms or a halogen substituted hydrocarbon group; n is a valuefrom 0 to 4. When n is at least 2, R^(f) may be the same or different.Examples of bisphenol compounds that may be represented by the formula(V), are resorcinol, substituted resorcinol compounds such as5-methylresorcin, 5-ethylresorcin, 5-propylresorcin, 5-butylresorcin,5-t-butylresorcin, 5-phenylresorcin, 5-cumylresorcin, or the like;catechol, hydroquinone, substituted hydroquinones, such as3-methylhydroquinone, 3-ethylhydroquinone, 3-propylhydroquinone,3-butylhydroquinone, 3-t-butylhydroquinone, 3-phenylhydroquinone,3-cumylhydroquinone, or the like; or combinations comprising at leastone of the foregoing bisphenol compounds.

Bisphenol compounds such as2,2,2′,2′-tetrahydro-3,3,3′,3′-tetramethyl-1,1′-spirobi-[IH-indene]-6,6′-diolrepresented by the following formula (VI) may also be used.

Suitable polycarbonates further include those derived from bisphenolscontaining alkyl cyclohexane units. Such polycarbonates have structuralunits corresponding to the formula (VII)

wherein R^(a)—R^(d) are each independently hydrogen, C₁-C₁₂ hydrocarbyl,or halogen; and R^(e)—R^(i) are each independently hydrogen, C₁-C₁₂hydrocarbyl. As used herein, “hydrocarbyl” refers to a residue thatcontains only carbon and hydrogen. The residue may be aliphatic oraromatic, straight-chain, cyclic, bicyclic, branched, saturated, orunsaturated. The hydrocarbyl residue may contain heteroatoms over andabove the carbon and hydrogen members of the substituent residue. Thus,when specifically noted as containing such heteroatoms, the hydrocarbylresidue may also contain carbonyl groups, amino groups, hydroxyl groups,or the like, or it may contain heteroatoms within the backbone of thehydrocarbyl residue. Alkyl cyclohexane containing bisphenols, forexample the reaction product of two moles of a phenol with one mole of ahydrogenated isophorone, are useful for making polycarbonate polymer swith high glass transition temperatures and high heat distortiontemperatures. Such isophorone bisphenol-containing polycarbonates havestructural units corresponding to the formula (VIII)

wherein R^(a)-R^(d) are as defined above. These isophorone bisphenolbased polymer s, including polycarbonate copolymers made containingnon-alkyl cyclohexane bisphenols and blends of alkyl cyclohexylbisphenol containing polycarbonates with non-alkyl cyclohexyl bisphenolpolycarbonates, are supplied by Bayer Co. under the APEC trade name. Thepreferred bisphenol compound is bisphenol A.

In one embodiment, the dihydroxy compound may be reacted with ahydroxyaryl-terminated poly(diorganosiloxane) to create apolycarbonate-polysiloxane copolymer. Preferably thepolycarbonate-poly(diorganosiloxane)copolymers are made by introducingphosgene under interfacial reaction conditions into a mixture of adihydroxy compound, such as BPA, and a hydroxyaryl-terminatedpoly(diorganosiloxane). The polymerization of the reactants can befacilitated by use of a tertiary amine catalyst or a phase transfercatalyst.

The hydroxyaryl-terminated poly(diorganosiloxane) can be made byeffecting a platinum catalyzed addition between a siloxane hydride ofthe formula (IX),

and an aliphatically unsaturated monohydric phenol wherein R⁴ is, forexample, C₍₁₋₈₎ alkyl radicals, haloalkyl radicals such astrifluoropropyl and cyanoalkyl radicals; aryl radicals such as phenyl,chlorophenyl and tolyl. R⁴ is preferably methyl, or a mixture of methyland trifluoropropyl, or a mixture of methyl and phenyl.

Some of the aliphatically unsaturated monohydric phenols, which can beused to make the hydroxyaryl-terminated poly(diorganosiloxane)s are, forexample, eugenol, 2-alkylphenol, 4-allyl-2-methylphenol,4-allyl-2-phenylphenol, 4-allyl-2-bromophenol, 4-allyl-2-t-butoxyphenol,4-phenyl-2-phenylphenol, 2-methyl-4-propylphenol,2-allyl-4,6-dimethylphenol, 2-allyl-4-bromo-6-methylphenol,2-allyl-6-methoxy-4-methylphenol, 2-allyl-4,6-dimethylphenol, or thelike, or a combination comprising at least one of the foregoing.

Typical carbonate precursors include the carbonyl halides, for examplecarbonyl chloride(phosgene), and carbonyl bromide; the bis-haloformates,for example the bis-haloformates of dihydric phenols such as bisphenolA, hydroquinone, or the like, and the bis-haloformates of glycols suchas ethylene glycol and neopentyl glycol; and the diaryl carbonates, suchas diphenyl carbonate, di(tolyl)carbonate, and di(naphthyl)carbonate.The preferred carbonate precursor for the interfacial reaction iscarbonyl chloride.

It is also possible to employ polycarbonates resulting from thepolymerization of two or more different dihydric phenols or a copolymerof a dihydric phenol with a glycol or with a hydroxy- or acid-terminatedpolyester or with a dibasic acid or with a hydroxy acid or with analiphatic diacid in the event a carbonate copolymer rather than ahomopolymer is desired for use. Generally, useful aliphatic diacids haveabout 2 to about 40 carbons. A preferred aliphatic diacid isdodecanedioic acid.

Branched polycarbonates, as well as blends of linear polycarbonate and abranched polycarbonate may also be used in the core layer. The branchedpolycarbonates may be prepared by adding a branching agent duringpolymerization. These branching agents may comprise polyfunctionalorganic compounds containing at least three functional groups, which maybe hydroxyl, carboxyl, carboxylic anhydride, haloformyl, andcombinations comprising at least one of the foregoing branching agents.Specific examples include trimellitic acid, trimellitic anhydride,trimellitic trichloride, tris-p-hydroxyphenylethane, isatin-bis-phenol,tris-phenol TC (1,3,5-tris((p-hydroxyphenyl)isopropyl)benzene),tris-phenol PA (4(4(1,1-bis(p-hydroxyphenyl)-ethyl)α,α-dimethylbenzyl)phenol), 4-chloroformylphthalic anhydride, trimesicacid, benzophenonetetracarboxylic acid, or the like, or combinationscomprising at least one of the foregoing branching agents. The branchingagents may be added at a level of about 0.05 to about 4.0 weight percent(wt %), based upon the total weight of the polycarbonate in a givenlayer.

In one embodiment, the polycarbonate may be produced by a meltpolycondensation reaction between a dihydroxy compound and a carbonicacid diester. Examples of the carbonic acid diesters that may beutilized to produce the polycarbonates are diphenylcarbonate,bis(2,4-dichlorophenyl)carbonate, bis(2,4,6-trichlorophenyl)carbonate,bis(2-cyanophenyl)carbonate, bis(o-nitrophenyl)carbonate,ditolylcarbonate, m-cresylcarbonate, dinaphthylcarbonate,bis(diphenyl)carbonate, diethylcarbonate, dimethylcarbonate,dibutylcarbonate, dicyclohexylcarbonate,bis(o-methoxycarbonylphenyl)carbonate,bis(o-ethoxycarbonylphenyl)carbonate,bis(o-propoxycarbonylphenyl)carbonate, bis-orthomethoxyphenylcarbonate,bis(o-butoxycarbonylphenyl)carbonate,bis(isobutoxycarbonylphenyl)carbonate,o-methoxycarbonylphenyl-o-ethoxycarbonylphenylcarbonate,biso-(tert-butoxycarbonylphenyl)carbonate,o-ethylphenyl-o-methoxycarbonylphenylcarbonate,p-(tertbutylphenyl)-o-(tert-butoxycarbonylphenyl)carbonate,bis-methylsalicylcarbonate, bis-ethylsalicylcarbonate,bis-propylsalicylcarbonate, bis-butylsalicylcarbonate,bis-benzylsalicylcarbonate, bis-methyl4-chlorosalicylcarbonate or thelike, or combinations comprising at least one of the foregoing carbonicacid diesters. The preferred carbonic acid diester is diphenylcarbonateor bis-methylsalicylcarbonate.

Preferably, the weight average molecular weight of the polycarbonate isabout 3,000 to about 1,000,000 grams/mole (g/mole). In one embodiment,the polycarbonate has a molecular weight of about 10,000 to about100,000 g/mole. In another embodiment, the polycarbonate has a molecularweight of about 20,000 to about 50,000 g/mole. In yet anotherembodiment, the polycarbonate has a molecular weight of about 25,000 toabout 35,000 g/mole.

The thermoplastic polymer is generally used in amounts of about 70 toabout 99.9 weight percent (wt %) based upon the weight of the corelayer. In one embodiment, the thermoplastic polymer is present in anamount of about 75 to about 99.7 wt %, based on the total weight of thecore layer. In another embodiment, the thermoplastic polymer is presentin an amount of about 80 to about 99.5 wt %, based on the total weightof the core layer. In yet another embodiment, the thermoplastic polymeris present in an amount of about 85 to about 97 wt %, based on the totalweight of the core layer.

The IR absorbing additives are generally fine particles of a metalboride or a boride such as such as lanthanum boride (LaB₆), praseodymiumboride (PrB₆), neodymium boride (NdB₆), cerium boride (CeB₆), gadoliniumboride (GdB₆), terbium boride (TbB₆), dysprosium boride (DyB₆), holmiumboride (HoB₆), yttrium boride (YB₆), samarium boride (SmB₆), europiumboride (EuB₆), erbium boride (ErB₆), thulium boride (TmB₆), ytterbiumboride (YbB₆), lutetium boride (LuB₆), strontium boride (SrB₆), calciumboride (CaB₆), titanium boride (TiB₂), zirconium boride (ZrB₂), hafniumboride (HfB₂), vanadium boride (VB₂), tantalum boride (TaB₂), chromiumborides (CrB and CrB₂), molybdenum borides (MoB₂, Mo₂B₅ and MoB),tungsten boride (W₂B₅), or the like, or combinations comprising at leastone of the foregoing borides.

It is desirable for the IR absorbing additives to be in the form ofnanosized particles prior to the dispersion into the polycarbonate.There is no particular limitation to the shape of the particles, whichmay be for example, spherical, irregular, plate-like or whisker like.The nanosized particles may generally have average largest dimensions ofless than or equal to about 200 nanometers (nm). In one embodiment, theparticles may have average largest dimensions of less than or equal toabout 150 nm. In another embodiment, the particles may have averagelargest dimensions of less than or equal to about 100 nm. In yet anotherembodiment, the particles may have average largest dimensions of lessthan or equal to about 75 nm. In yet another embodiment, the particlesmay have average largest dimensions of less than or equal to about 50nm. As stated above, the nanosized particles may generally have averagelargest dimensions of less than or equal to about 200 nm. In oneembodiment, more than 90% of the particles have average largestdimensions less than or equal to about 200 nm. In another embodiment,more than 95% of the particles have average largest dimensions less thanor equal to about 200 nm. In yet another embodiment, more than 99% ofthe particles have average largest dimensions less than or equal toabout 200 nm. Bimodal or higher particle size distributions may be used.

The IR absorbing additives are generally used in amounts of about 0.001gram/square meter (g/m²) to about 2.0 g/m². In one embodiment, the IRabsorbing additive may be used in amounts of about 0.03 to about 1.0g/m². In another embodiment, the IR absorbing additive may be used inamounts of about 0.05 to about 0.75 g/m². In yet another embodiment, theIR absorbing additive may be used in amounts of about 0.09 to about 0.36g/m².

The IR absorbing additives are generally used in amounts of about 0.02ppm to about 3000 ppm based on the total weight of the core layer. Inone embodiment, the IR absorbing additive may be used in amounts ofabout 1 ppm to about 1500 ppm, based on the total weight of the corelayer. In another embodiment, the IR absorbing additive may be used inamounts of about 1.5 ppm to about 1250 ppm based on the total weight ofthe core layer. In yet another embodiment, the IR absorbing additive maybe used in amounts of about 2.5 ppm to about 600 ppm, based on the totalweight of the core layer and depending on the thickness of the sheet. Inone embodiment, the core layer may contain thermal stabilizers tocompensate for the increase in temperature brought on by the interactionof the IR light with the IR absorbing additives. Additionally theaddition of thermal stabilizers protects the material during processingoperations such as melt blending. In general, a layer of polycarbonatecontaining the IR absorbing additives may experience an increase intemperature of up to about 20° C., upon exposure to light. The additionof thermal stabilizers to the core layer improves the long term agingcharacteristics and increases the life cycle of the multilayer sheet. Inanother embodiment, UV stabilizers may also be optionally added to thecore layer to prevent against UV degradation. Suitable thermalstabilizers include phosphites, phosphonites, phosphines, hinderedamines, hydroxyl amines, phenols, acryloyl modified phenols,hydroperoxide decomposers, benzofuranone derivatives, or the like, orcombinations comprising at least one of the foregoing thermalstabilizers. Suitable thermal stabilizers that are commerciallyavailable are IRGAPHOS 168, DOVERPHOS S-9228, ULTRANOX 641, whilesuitable commercially available UV stabilizers are TINUVIN 329, TINUVIN234, TINUVIN 350, TINUVIN 360 or UVINOL 3030. If desirable, an optionalco-stabilizer such as a cyclo aliphatic epoxy polymer or IRGANOX 1076may also be added to improve thermal stability of the core layer. Thepreferred thermal stabilizers are phosphites.

It is generally desirable to add the thermal stabilizer in an amount ofabout 0.001 to about 3 wt %, based on the total weight of the corelayer. In one embodiment, the thermal stabilizer may be added in amountsof about 0.002 to about 0.5 wt %, based on the total weight of the corelayer. In another embodiment, the thermal stabilizer may be added inamounts of about 0.005 to about 0.2 wt %, based on the total weight ofthe core layer. In yet another embodiment, the thermal stabilizer may beadded in amounts of about 0.01 to about 0.1 wt %, based on the totalweight of the core layer. If a co-stabilizer is added, it is generallydesirable to add it in amount of about 0.001 to about 2 wt %, based onthe total weight of the core layer.

In addition to the thermal stabilizers and the UV stabilizer, otheradditives such as mold release agents, pigments, dyes, impact modifiers,lubricants, anti-oxidants, anti-microbials, flame retardants, visualeffect additives, fibers such as carbon fibers, glass fibers, carbonnanotubes, or the like; antistatic agents, plasticizers, fillers such asfumed silica, aerogels, carbon black, or the like; can be added to boththe core and the cap layers.

It is generally desirable for the core layer to have a thickness ofabout 0.5 to about 30 mm. In one embodiment, the core layer may have athickness of about 0.75 to about 25 mm. In another embodiment, the corelayer may have a thickness of about 0.85 to about 20 mm. In yet anotherembodiment, the core layer may have a thickness of about 1 to about 15mm.

As stated above, the multilayered sheet may comprise a single cap layerdisposed on an and in intimate contact with the core layer.Alternatively, the multilayered sheet may comprise two cap layers, onecap layer disposed on either surface of the core layer and in intimatecontact with it. The cap layer also generally comprises a thermoplasticpolymer. Suitable thermoplastic polymers are polycarbonate,copolyestercarbonates, or blends of polyesters with polycarbonates. Thepolyesters may be cycloaliphatic polyesters, polyarylates or acombination of cycloaliphatic polyesters with polyarylates.

Cycloaliphatic polyesters suitable for use in the cap layer are thosethat are characterized by optical transparency, improved weatherability,chemical resistance, and low water absorption. It is also generallydesirable that the cycloaliphatic polyesters have good meltcompatibility with the thermoplastic polymers used in the core layer. Inan exemplary embodiment, it is preferred to use a cycloaliphaticpolyester that displays good melt compatibility with the polycarbonateused in the core layer. Cycloaliphatic polyesters are generally preparedby reaction of a diol with a dibasic acid or derivative. The diolsuseful in the preparation of the cycloaliphatic polyester polymers foruse as the high quality optical sheets are straight chain, branched, orcycloaliphatic, preferably straight chain or branched alkane diols, andmay contain from 2 to 12 carbon atoms.

Suitable examples of diols include ethyleneglycol, propyleneglycol suchas 1,2- and 1,3-propyleneglycol, and the like; butanediol such as 1,3-and 1,4-butanediol, and the like; diethyleneglycol,2,2-dimethyl-1,3-propanediol, 2-ethyl, 2-methyl, 1,3-propanediol, 1,3-and 1,5-pentanediol, dipropylene glycol, 2-methyl-1,5-pentainediol,1,6-hexanediol, 1,4-cyclohexanedimethanol and particularly its cis- andtrans-isomers, triethyleneglycol, 1,10-decanediol, and combinationscomprising at least one of the foregoing diols. Particularly preferredis dimethanolbicyclooctane, dimethanoldecalin, a cycloaliphaticdiol orchemical equivalents thereof, and particularly 1,4-cyclohexanedimethanolor its chemical equivalents. If 1,4-cyclohehanedimethanol is to be usedas the diol component, it is generally preferred to use a mixture ofcis- to trans-isomes in ratios of about 1:4 to about 4:1. Within thisrange, it is generally desired to use a ratio of cis- to trans-isomersof about 1:3.

The diacids useful in the preparation of the cycloaliphatic polyesterpolymers are aliphatic diacids that include carboxylic acids having twocarboxyl groups each of which are attached to a saturated carbon in asaturated ring. Suitable examples of cycloaliphatic acids includedecahydronaphthalenedicarboxylic acid, norbomenedicarboxylic acids,bicyclooctanedicarboxylic acids. Preferred cycloaliphaticdiacids are1,4-cyclohexanedicarboxylic acid and trans-1,4-cyclohexanedicarboxylicacids. Linear aliphatic diacids are also useful provided the polyesterhas at least one monomer containing a cycloaliphatic ring. Illustrativeexamples of linear aliphatic diacids are succinic acid, adipic acid,dimethylsuccinic acid, and azelaic acid. Mixtures of diacid and diolsmay also be used to make the cycloaliphatic polyesters.

Cyclohexanedicarboxylic acids and their chemical equivalents can beprepared, for example, by the hydrogenation of cycloaromatic diacids andcorresponding derivatives such as isophthalic acid, terephthalic acid ornaphthalenic acid in a suitable solvent (e.g., water or acetic acid) atroom temperature and at atmospheric pressure using catalysts such asrhodium supported on a carrier comprising carbon and alumina. They mayalso be prepared by the use of an inert liquid medium wherein an acid isat least partially soluble under reaction conditions and a catalyst ofpalladium or ruthenium in carbon or silica is used.

Generally, during hydrogenation, two or more isomers are obtained inwhich the carboxylic acid groups are in cis- or trans-positions. Thecis- and trans-isomers can be separated by crystallization with orwithout a solvent, for example, n-heptane, or by distillation. Thecis-isomer tends to be more miscible, however, the trans-isomer hashigher melting and crystallization temperatures and is especiallypreferred. Mixtures of the cis- and trans-isomers may also be used, andpreferably when such a mixture is used, the trans-isomer will preferablycomprise at least about 75 wt % and the cis-isomer will comprise theremainder based on the total weight of cis- and trans-isomers combined.When a mixture of isomers or more than one diacid is used, a copolyesteror a mixture of two polyesters may be used as the cycloaliphaticpolyester polymer.

Chemical equivalents of these diacids including esters may also be usedin the preparation of the cycloaliphatic polyesters. Suitable examplesof the chemical equivalents of the diacids are alkyl esters, e.g.,dialkyl esters, diaryl esters, anhydrides, acid chlorides, acidbromides, and the like, as well as combinations comprising at least oneof the foregoing chemical equivalents. The preferred chemicalequivalents comprise the dialkyl esters of the cycloaliphatic diacids,and the most preferred chemical equivalent comprises the dimethyl esterof the acid, particularly dimethyl-trans-1,4-cyclohexanedicarboxylate.

Dimethyl-1,4-cyclohexanedicarboxylate can be obtained by ringhydrogenation of dimethylterephthalate, and two isomers having thecarboxylic acid groups in the cis- and trans-positions are obtained. Theisomers can be separated, the trans-isomer being especially preferred.Mixtures of the isomers may also be used as detailed above.

The polyester polymers are generally obtained through the condensationor ester interchange polymerization of the diol or diol chemicalequivalent component with the diacid or diacid chemical equivalentcomponent and having recurring units of the formula (X):

wherein R³ represents an alkyl or cycloalkyl radical containing 2 to 12carbon atoms and which is the residue of a straight chain, branched, orcycloaliphatic alkane diol having 2 to 12 carbon atoms or chemicalequivalents thereof; and R⁴ is an alkyl or a cycloaliphatic radicalwhich is the decarboxylated residue derived from a diacid, with theproviso that at least one of R³ or R⁴ is a cycloalkyl group.

A preferred cycloaliphatic polyester ispoly(1,4-cyclohexane-dimethanol-1,4-cyclohexanedicarboxylate) (PCCD)having recurring units of formula (XI)

wherein in the formula (IX) R³ is a cyclohexane ring, and wherein R⁴ isa cyclohexane ring derived from cyclohexanedicarboxylate or a chemicalequivalent thereof and is selected from the cis- or trans-isomer or amixture of cis- and trans-isomers thereof. Cycloaliphatic polyesterpolymers can be generally made in the presence of a suitable catalystsuch as a tetra(2-ethyl hexyl)titanate, in a suitable amount, generallyabout 50 to 400 ppm of titanium based upon the total weight of the finalproduct.

PCCD is generally completely miscible with the polycarbonate. It isgenerally desirable for a polycarbonate-PCCD mixture to have a meltvolume rate of greater than or equal to about 5 cubic centimeters/10minutes (cc/10 min or ml/10 min) to less than or equal to about 150cubic centimeters/10 minutes when measured at 265° C., at a load of 2.16kilograms and a four minute dwell time. Within this range, it isgenerally desirable to have a melt volume rate of greater than or equalto about 7, preferably greater than or equal to about 9, and morepreferably greater than or equal to about 10 cc/10 min when measured at265° C., at a load of 2.16 kilograms and a four minute dwell time. Alsodesirable within this range, is a melt volume rate of less than or equalto about 125, preferably less than or equal to about 110, and morepreferably less than or equal to about 100 cc/10 minutes.

Other preferred cycloaliphatic polyesters that may be mixed with thepolycarbonate are polyetheleneterephthalate (PET),polybutyleneterephthalate (PBT), poly(trimethyleneterephthalate) ( PTT),poly(cyclohexanedimethanol-co-ethyleneterephthalate) (PETG),poly(ethylenenaphthalate) (PEN), and poly(butylenenaphthalate) (PBN).

Another preferred polyester that may be mixed with other polymers arepolyarylates. Polyarylates generally refers to polyesters of aromaticdicarboxylic acids and bisphenols. Polyarylate copolymers that includecarbonate linkages in addition to the aryl ester linkages, are termedpolyester-carbonates, and may also be advantageously utilized in themixtures. The polyarylates can be prepared in solution or by the meltpolymerization of aromatic dicarboxylic acids or their ester formingderivatives with bisphenols or their derivatives.

In general, it is preferred for the polyarylates to comprise at leastone diphenol residue in combination with at least one aromaticdicarboxylic acid residue. The preferred diphenol residue, illustratedin formula (XII), is derived from a 1,3-dihydroxybenzenemoiety, referredto throughout this specification as resorcinol or resorcinol moiety.Resorcinol or resorcinol moieties include both unsubstituted1,3-dihydroxybenzene and substituted 1,3-dihydroxybenzenes.

In formula (X), R is at least one of C₁₋₁₂ alkyl or halogen, and n is 0to 3. Suitable dicarboxylic acid residues include aromatic dicarboxylicacid residues derived from monocyclic moieties, preferably isophthalicacid, terephthalic acid, or mixtures of isophthalic and terephthalicacids, or from polycyclic moieties such as diphenyldicarboxylic acid,diphenyletherdicarboxylic acid, and naphthalene-2,6-dicarboxylic acid,and the like, as well as combinations comprising at least one of theforegoing polycyclic moieties. The preferred polycyclic moiety isnaphthalene-2,6-dicarboxylic acid.

Preferably, the aromatic dicarboxylic acid residues are derived frommixtures of isophthalic and/or terephthalic acids as generallyillustrated in formula (XIII).

Therefore, in one embodiment the polyarylates comprise resorcinolarylate polyesters as illustrated in formula (XIV) wherein R and n arepreviously defined for formula (XI).

wherein R is at least one of C₁₋₁₂ alkyl or halogen, n is 0 to3, and mis at least about 8. It is preferred for R to be hydrogen. Preferably, nis zero and m is about 10 and about 300. The molar ratio of isophthalateto terephthalate is about 0.25:1 to about 4.0:1.

In another embodiment, the polyarylate comprises thermally stableresorcinol arylate polyesters that have polycyclic aromatic radicals asshown in formula (XV)

wherein R is at least one of C₁₋₁₂ alkyl or halogen, n is 0 to 3, and mis at least about 8.

In another embodiment, the polyarylates are copolymerized to form blockcopolyestercarbonates, which comprise carbonate and arylate blocks. Theyinclude polymers comprising structural units of the formula (XVI)

wherein each R¹ is independently halogen or C₁₋₁₂ alkyl, m is at least1, p is about 0 to about 3, each R² is independently a divalent organicradical, and n is at least about 4. Preferably n is at least about 10,more preferably at least about 20 and most preferably about 30 to about150. Preferably m is at least about 3, more preferably at least about 10and most preferably about 20 to about 200. In an exemplary embodiment mis present in an amount of about 20 and 50.

It is generally desirable for the weight average molecular weight of thepolyester to be about 500 to about 1,000,000 grams/mole (g/mole). In oneembodiment, the polyester has a weight average molecular weight of about10,000 to about 200,000 g/mole. In another embodiment, the polyester hasa weight average molecular weight of about 30,000 to about 150,000g/mole. In yet another embodiment, the polyester has a weight averagemolecular weight of about 50,000 to about 120,000 g/mole. An exemplarymolecular weight for the polyester utilized in the cap layer is 60,000and 120,000 g/mole. These molecular weights are determined against apolystyrene standard.

In one embodiment, it is desirable to match the melt viscosity of thethermoplastic polymer used in the core layer with the melt viscosity ofthe thermoplastic polymer used in the cap layer during the formation ofthe multilayer sheet. In another embodiment, it is desirable for themelt viscosity of the thermoplastic polymer used in the cap layer to beequal to the melt viscosity of the thermoplastic polymer used in thecore layer, at the point of initial contact of the two melts during theformation of the multilayer sheet. In yet another embodiment, it isdesirable for the melt viscosity of the thermoplastic polymer used inthe cap layer to be within 1% of the melt viscosity of the thermoplasticpolymer used in the core layer, at the point of initial contact of thetwo melts during the formation of the multilayer sheet. In yet anotherembodiment, it is desirable for the melt viscosity of the thermoplasticpolymer used in the cap layer to be within 5% of the melt viscosity ofthe thermoplastic polymer used in the core layer, at the point ofinitial contact of the two melts during the formation of the multilayersheet. In yet another embodiment, it is desirable for the melt viscosityof the thermoplastic polymer used in the cap layer to be within 10% ofthe melt viscosity of the thermoplastic polymer used in the core layer,at the point of initial contact of the two melts during the formation ofthe multilayer sheet. In yet another embodiment, it is desirable for themelt viscosity of the thermoplastic polymer used in the cap layer to bewithin 20% of the melt viscosity of the thermoplastic polymer used inthe core layer, at the point of initial contact of the two melts duringthe formation of the multilayer sheet.

The polyester and/or copolyestercarbonates are generally used in amountsof about 70 to about 99.9 weight percent (wt %) based upon the weight ofthe cap layer. Within this range, an amount of greater than or equal toabout 75, preferably greater than or equal to about 80, and morepreferably greater than or equal to about 85 wt % may be used, basedupon the weight of the cap layer. Also desirable within this range, isan amount of greater than or equal to about 98, preferably greater thanor equal to about 97, and more preferably greater than or equal to about95 wt % may be used, based upon the weight of the cap layer.

The cap layer generally comprises a suitable UV absorber. Suitable UVabsorbers are benzophenones such as 2,4 dihydroxybenzophenone,2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone,4-dodecyloxy-2hydroxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone,2,2′dihydroxy-4methoxybenzophenone,2,2′dihydroxy-4,4′dimethoxybenzophenone,2,2′dihydroxy-4methoxybensophenone, 2,2′, 4,4′tetrahydroxybenzophenone,2-hydroxy-4-methoxy-5sulfobenzophenone,2-hydroxy-4-methoxy-2′-carboxybenzophenone,2,2′dihydroxy-4,4′dimethoxy-5sulfobenzophenone,2-hydroxy-4-(2-hydroxy-3-methylaryloxy)propoxybenzophenone,2-hydroxy-4chlorobenzopheone, or the like; benzotriazoles such as2,2′-(hydroxy-5-methylphenyl)benzotriazole,2,2′-(hydroxy-3′,5′-ditert-butylphenyl)benzotriazole, and2,2′-(hydroxy-X-tert, butyl-5′-methyl-phenyl) benzotriazole, or thelike; salicylates such as phenyl salicylate, carboxyphenyl salicylate,p-octylphenyl salicylate, strontium salicylate, p-tert butylphenylsalicylate, methyl salicylate, dodecyl salicylate, or the like; and alsoother ultraviolet absorbents such as resorcinol monobenzoate,2′ethylhexyl-2-cyano, 3-phenylcinnamate,2-ethyl-hexyl-2-cyano-3,3acrylate, ethyl-2-cyano-3,3-diphenyl acrylate,[2-2′-thiobis(4-t-octylpenolate)-1-n-butylamine, or the like, orcombinations comprising at least one of the foregoing UV absorbers. Apreferred UV absorber for use in the cap layer is UVNUL 3030,commercially available from BASF.

The UV absorbers are generally used in amounts of about 5 wt % to about15 wt %, based upon the weight of the cap layer. In one embodiment, theUV absorber may be used in an amount of 7 to about 14 wt %, based on thetotal weight of the cap layer. In yet another embodiment, the UVabsorber may be used in an amount of 8 to about 12 wt %, based on thetotal weight of the cap layer. In one embodiment, the UV absorber may beused in an amount of 9 to about 11 wt %, based on the total weight ofthe cap layer.

It is generally desirable for the cap layer to have an average thicknessof about 10 to about 120 micrometers. In one embodiment, the cap layermay have a thickness of about 15 to about 100 micrometers. In anotherembodiment, the cap layer may have a thickness of about 20 to about 90micrometers. In yet another embodiment, the cap layer may have athickness of about 25 to about 80 micrometers.

The multilayer sheet may generally be produced by extrusion followed bylaminating the sheets in a roll mill or a roll stack. The extrusion ofthe individual layers of the multilayered sheet may be performed in asingle screw extruder or in a twin screw extruder. It is desirable toextrude the layers in a single screw extruder and to laminate the layersin a roll mill. It is more desirable to co-extrude the layers in asingle screw extruder or twin screw extruder and to optionally laminatethe layers in a roll mill. The roll mill may be either a two roll orthree roll mill, as is desired. Co-extrusion of the layers by singlescrew extruders is generally desirable for the manufacturing of themultilayered sheet.

In one embodiment, in the extrusion of the core layer and the cap layer,the additives (e.g., IR absorbing additive and UV absorber) may be addedto the extruder along with the thermoplastic polymer at the feed throat.In another embodiment, in the extrusion of the core layer and the caplayer, the additives may be added to the extruder in the form of amasterbatch. While the thermoplastic polymer is fed to the throat of theextruder, the masterbatch may be fed either at the throat of theextruder or downstream or the throat. In one exemplary embodiment, inthe production of the core layer, the thermoplastic polymer is fed tothe throat of a single screw extruder while the IR absorbing additive isadded in masterbatch form downstream of the feed throat. In anotherexemplary embodiment, in the production of the cap layer, thethermoplastic polymer is fed to the throat of a single screw extruderwhile the UV absorber is added in masterbatch form downstream of thefeed throat.

In one embodiment, the desired composition for the core layer and thecap layer may be separately precompounded prior to coextrusion. In thisevent, the precompounded materials may be first melt blended in a twinscrew extruder, single screw extruder, buss kneader, roll mill, or thelike, prior to being formed into a suitable shapes such as pellets,sheets, and the like, for further co-extrusion. The precompounded coreand cap layer compositions may ten be fed into the respective extrudersfor co-extrusion.

As stated above, it is desirable to co-extrude the cap and the corelayer. In one embodiment, in one manner of co-extruding of themultilayered sheet, the melt streams (extrudates) from the variousextruders are fed into a feed block die where the various melt streamsare combined before entering the die. In another embodiment, the meltstreams from the various extruders are fed into a multi-manifoldinternal combining die. The different melt streams enter the dieseparately and join just inside the final die orifice. In yet anotherembodiment, the melt streams from the various extruders are fed into amulti-manifold external combining die. The external combining dies havecompletely separate manifolds for the different melt streams as well asdistinct orifices through which the streams leave the die separately,joining just beyond the die exit. The layers are combined while stillmolten and just downstream of the die. An exemplary die used in theproduction of the multilayered sheet is a feed block die. In anexemplary embodiment, the extruders used for the co-extrusion of the capand core layers are single screw extruders respectively. The co-extrudedsheet may optionally be calendared in a roll mill if desired. Themultilayered sheet generally has a thickness of about 0.5 to about 35millimeters.

It is desirable for the multilayered sheet to absorb an amount ofgreater than or equal to about 90% of all the IR radiation incident uponthe surface of the sheet. In one embodiment, the multilayered sheet mayabsorb an amount of greater than or equal to about 60% of all the IRradiation incident upon the surface of the sheet. In another embodiment,the multilayered sheet may absorb an amount of greater than or equal toabout 50% of all the IR radiation incident upon the surface of thesheet. In yet another embodiment, the multilayered sheet may absorb anamount of greater than or equal to about 40% of all the IR radiationincident upon the surface of the sheet. In yet another embodiment, themultilayered sheet may absorb an amount of greater than or equal toabout 20% of all the IR radiation incident upon the surface of thesheet. In yet another embodiment, the multilayered sheet may absorb anamount of greater than or equal to about 5% of all the IR radiationincident upon the surface of the sheet.

It is desirable for the multilayered sheet to absorb an amount ofgreater than or equal to about 90% of all the UV radiation incident uponthe surface of the sheet. In one embodiment, the multilayered sheet mayabsorb an amount of greater than or equal to about 60% of all the UVradiation incident upon the surface of the sheet. In another embodiment,the multilayered sheet may absorb an amount of greater than or equal toabout 50% of all the UV radiation incident upon the surface of thesheet. In yet another embodiment, the multilayered sheet may absorb anamount of greater than or equal to about 40% of all the UV radiationincident upon the surface of the sheet. In yet another embodiment, themultilayered sheet may absorb an amount of greater than or equal toabout 20% of all the UV radiation incident upon the surface of thesheet. In yet another embodiment, the multilayered sheet may absorb anamount of greater than or equal to about 5% of all the UV radiationincident upon the surface of the sheet.

While it is generally desirable for the multilayer sheet to absorb asmuch electromagnetic radiation as possible in the UV and IR regions ofthe electromagnetic spectrum, it is desirable for the multilayered sheetto be transparent to light in the visible region of the electromagneticspectrum. The visible region of the electromagnetic spectrum generallyhas wavelengths of about 400 to about 700 nm. It is desirable for thesheet to have a transmissivity to light in the visible region of greaterthan or equal to about 20%. In one embodiment, it is desirable for thesheet to have a transmissivity to light in the visible region of greaterthan or equal to about 30%. In another embodiment, it is desirable forthe sheet to have a transmissivity to light in the visible region ofgreater than or equal to about 40%. In yet another embodiment, it isdesirable for the sheet for have a transmissivity of greater than orequal to about 50%.

It is also desirable for the multilayered sheet to have a haze of lessthan or equal to about 5%. In one embodiment, the haze may be less thanor equal to about 2%. In another embodiment, the haze may be less thanor equal to about 1.8%. In another embodiment, the haze may be less thanor equal to about 1.6%.

If the resulting multilayer sheet is in the form of a multiwall sheet,it is generally desirable to have a haze of less than 25%. In oneembodiment, the haze may be less than or equal to about 20%. In anotherembodiment, the haze may be less than or equal to about 15%. In anotherembodiment, the haze may be less than or equal to about 10%.

The multilayer sheet thus produced may be advantageously used inautomobiles, residential and office buildings or other areas where heatproduced by exposure to IR radiation is undesirable. In one embodiment,the sheets may be used as roofing or glazing materials, after beingco-extruded as multiwall sheets with air channels in between the wallsas shown in FIG. 3. FIG. 3 is a schematic depiction of a multiwall sheetwherein the respective sheets are separated by brackets and having airpockets in between the brackets. The sheet thickness is also depicted inthe FIG. 3 and encompasses the brackets as well as the individualmultilayer sheets. The brackets may also be made of a thermoplasticpolymer such as those described above. In one embodiment, the bracketmay be manufactured from polycarbonate, polyester, orpolyestercarbonate-polyester.

The multilayer sheet thus formed may also be subjected to additionalprocessing such as thermoforming, vacuum molding, blow molding, shaping,and the like, to produce materials having different shapes andgeometries.

The following examples, which are meant to be exemplary, not limiting,illustrate compositions and methods of manufacturing some of the variousembodiments of the multilayered sheets using various materials andapparatus.

EXAMPLES Comparative Example

This example along with the following Example 1 was undertaken todemonstrate the benefits of incorporating the IR absorbing additive inthe core layer versus the cap layer. These examples were also undertakento demonstrate the benefits of placing the cap layer (containing UVabsorber) on the surface of the core layer (containing an IR absorbingadditive) in such a manner that when the multilayer sheet is subjectedto solar radiation, the radiation contacts the cap layer prior tocontacting the core layer. In these examples, a 3 mm multilayered sheethaving a cap layer (comprising polycarbonate with LaB₆ (IR absorbingadditive) and a UV absorber) disposed upon a polycarbonate layer wascompared with a multilayered sheet having the cap layer containing a UVabsorber disposed upon a core layer containing an IR absorbing additive.The comparative example discusses the results of placing the IRabsorbing additive (LaB₆) in the cap layer, while the following Example1 discusses the beneficial results of placing the IR absorbing additive(LaB₆) in the core layer.

The cap layer thickness was about 60 micrometers, though thicknessvariations caused the cap layer thickness to vary from about 50 to about80 micrometers. The composition and construction of the cap layer aswell as the core layer are detailed below.

LaB₆ in the Cap Layer

Both the cap and the core layer have polycarbonate as the thermoplasticpolymer. The polycarbonate was a linear bisphenol A polycarbonate havinga weight average molecular weight of 30,000 g/mole.

The cap layer contains 0.18 g/m² of LaB₆, 10% Tinuvin 234 and 0.1%Irgafos 168, with the remainder being bisphenol a polycarbonate. TheLaB₆ was obtained from a masterbatch containing 0.25 wt % LaB₆ in linearbisphenol A polycarbonate having a weight average molecular weight of30,000 g/mole. The aforementioned ingredients were procompounded in atwin screw extruder to form a cap layer precompound.

The core layer was first precompounded in a twin screw extruder. Thecore layer contains 99.75 wt % linear bisphenol A polycarbonate having aweight average molecular weight of 30,000 g/mole, 0.1 wt %pentaerythritoltetrastearate, 0.1 wt % Tinuvin 234 and 0.05 wt % Irgafos168. The core and cap layer precompounds were then co-extruded in thefollowing manner to produce the multilayer sheet.

The extruder used for extruding the core layer was a Werner andPfleiderer ZSK extruder 133 mm (twin screw extruder). The barreltemperatures were set at about 200 to 280° C. respectively. The dietemperature was 250° C. and the screw speed was 85 rpm. Five barrelshaving temperatures of 250, 260, 260, 270, 280° C. from feed throat todie respectively. The zone temperatures of the extruder used for makingthe cap layers (Macgi, Single Screw extruder having a 45 mm barreldiameter) were set between 200 and 280° C. and the screw speed was 58rpm. Six barrels were used in each of the single screw extruders withthe barrel temperatures set at 245, 255, 230, 230, 270, 280° C.respectively. The aforementioned barrel temperatures are, in order, fromthe feed throat to the feed block of the single screw extruderrespectively. Some characteristics of the core layer are given in Table1.

In the extrusion of the core and cap layers, pre-compounded pelletshaving the requisite compositions as detailed above, were fed to theextruder via the feed throat. The extrudate from the respectiveextruders was fed to a feed block die to from the co-extruded multilayersheet. Light transmission and haze were measured according to ASTM D1003, while the lab color was measured according to CIE lab DIN 5033.the results are shown in Table 1 below. TABLE 1 Cap-layer- Sample pointthickness across width Top cap layer (mm) (micron) LT (%) b-value colorHaze (%) Solar Transmission (%)  25 61.2 59.8 12.7 7.6 49.6  75 74.155.6 14.9 8.4 44.9 125 67.6 57.7 13.8 8 47.1 175 64.4 58.7 13.3 7.8 48225 80.5 53.4 15.9 8.7 42.6 275 67.6 57.7 13.8 8 46 325 51.5 63 11.1 7.152.4 375 64.4 58.7 13.3 7.8 48.4 425 64.4 58.7 13.3 7.8 47.3 475 67.657.7 13.8 8 46.1 525 64.4 58.7 13.3 7.8 47.3 575 54.7 61.9 11.6 7.3 50.8625 54.7 61.9 11.6 7.3 50.6 675 58 60.9 12.2 7.5 49.3 725 67.6 57.7 13.88 46.2 775 61.2 59.8 12.7 7.6 48.2 825 54.7 61.9 11.6 7.3 50.3 850 5860.9 12.2 7.5 49.6 Variation 51.5-80.5 53.4-63 11.1-15.9 7.1-8.742.6-52.4 Standard deviation 7.3 2.4 1.2 0.4 2.4

From the above table it may be seen that there is a wide variation inthe light transmission (LT) of about 53.4 to about 63%. Similarlyplacing the IR absorbing additive in the cap layer shows that themultilayer sheet has high levels of haze of greater than 7% and widevariations in the level of solar transmission.

Example 1

As stated above, this example demonstrates the efficacy of incorporatingthe LaB₆ in the core layer. A 3-layered multi layered sheet having itscore layer containing the LaB₆ in the amount shown for Sample #1 inTable 1 was coextruded with a UV cap layer. The sheet contains two caplayers and one core layer. The core layer was disposed between the twocap layers.

The cap layer of the 3-layered sheet was made in the form of apre-compound that contains 10 wt % UV absorber (Tinuvin 234), 0.1 wt %heat stabilizer (Irgafos 168) and 89.9% linear bipshenol Apolycarbonate.

The core layer was first precompounded by feeding and mixing thefollowing product streams: 16 wt % of a LaB₆ masterbatch containing0.032 wt % by weight of LaB₆, 0.05% Irgafos 168 and 99.918% linearpolycarbonate having a weight average molecular weight of 30,000 to31,000 g/mole. Secondly 5 wt % of a UV concentrate consisting of 97.5 wt% linear polycarbonate having a weight average molecular weight of30,000 g/mole, 2 wt % Tinuvin 234 and 0.1 wt % Irgafos 168. Theremainder was constituted by 79 wt % linear polycarbonate having aweight average molecular weight of 30,000 g/mole.

The respective pre-compounds were then fed to the respective extrudersas detailed in the Comparative Example to produce the multilayer sheet.The results are shown in the Tables 2 and 3. Table 2 depicts some of thecharacteristics of the multilayer sheet containing the LaB₆ in the corelayer. Table 3 shows the results obtained for the multilayered sheethaving the UV absorbers in the cap layer and the IR absorbing additivesin the core layer. In both cases, the cap layer was first contacted bythe impinging radiation. TABLE 2 LaB₆ Solar Shading Sample # conc. LT %ST % factor Coeff. Haze L a b 1 0.18 g/m² 62.0 50.8 1.21 0.58 1.4 82.3−6.4 12.5LT % = light TransmissionST % = Total Solar TransmissionSolar Factor = Light to Solar gain ratio = Total visible LightTransmission/Total Solar Transmission.Shading coefficient = total Solar Transmission/87

TABLE 3 Sample point across width b value Haze Solar (mm) LT % color (%)Transmission (%)  25 62.2 12.5 1.6 50.8  75 62.1 12.6 1.5 51 125 62.212.5 1.4 51.1 175 62.1 12.5 1.4 50.2 225 62.2 12.6 1.4 51.2 275 62.212.6 1.4 51 325 62.1 12.6 1.4 51.1 375 62.1 12.6 1.4 50.9 425 62.1 12.61.4 50.8 475 62.1 12.6 1.5 51 525 62 12.6 1.4 50.8 575 62 12.6 1.4 50.9625 62 12.6 1.4 50.8 675 62 12.6 1.4 51.2 725 62 12.6 1.4 51.1 775 61.912.6 1.4 50.9 825 61.9 12.6 1.4 50.9 850 61.9 12.6 1.5 51 Variation61.9-62.2 12.5-12.6 1.4-1.6 50.8-51.2 Standard deviation 0.1 0.06 0.0180.2

From the Tables 1 (comparative example) and 3 (present example), it maybe seen that having the IR absorbing additive, LaB₆, in the cap layer,causes a big variation in the percent light transmission (LT %), and thepercent haze, when compared with the multilayered sheet having the IRabsorbing additive in the core layer. From Table 3, it may also be seenthat the variations in the percent light transmission haze and color aresmaller than those for the samples of Table 1. Since it is generallydesirable to have the haze as low as possible, dispersing the IRabsorbing additive in the core layer produces a superior product over aproduct where the IR absorbing additive is added to the cap layer. FIG.4 represents photographs of an object taken through two multilayersheets, one multilayer sheet contained LaB₆ in the core layer, while theother had LaB₆ in the cap layer. From this figure it may be clearly seenthat while the object can be clearly seen through the multilayer sheetcontaining the LaB₆ in the core layer, it is barely visible through themultilayer sheet containing the LaB₆ in the cap layer. It clearly showsthe visible variation in color when LaB₆ is used in the cap layer.

During this test several other observations were made. As noted abovethickness variations of ±20 micrometers were observed in the thicknessof the cap layer. In order to have an acceptable IR absorption, a targetamount of 0.18 grams of LaB₆/m² of polycarbonate was utilized. When thisamount of IR absorbing additive is added to a 60 micrometer cap layerrather than a 3 to 6 millimeter core layer, its concentration is muchhigher in the cap layer, thus leading to an unacceptable level of hazein the multilayer sheet. Additionally, to protect polycarbonate from UVaging, a UV protective coating or UV adsorber containing cap layer isused on the multi layered sheet. A certain concentration of UV absorbersis needed to reach an acceptable level for the UV protection of PC. Onecould envision reducing the problem of thickness variation of the caplayer and thereby the observed transmission variations by using athicker cap layer, for example, a cap layer having a thickness of 500micrometers (0.5 mm). However, apart from practical problems of makingsuch a cap layer, the need for a high UV concentration throughout thecap layer would increase the cost of the entire multilayer sheet.

Example 2

This example was undertaken to study the effect of thermoforming themultilayer sheet, on the percent light transmission, solar factor,shading coefficient, and haze. Two 3 millimeter multilayer sheets havingLaB₆ concentrations of 0.09 and 0.18 g/M² respectively were thermoformedover the device shown in FIG. 5. Lab color measurements were madeaccording CIE lab DIN 5033; solar transmission measurements were madeaccording to ISO9050; haze and light transmission were measuredaccording to ASTM D1003. Upon thermoforming the multilayer sheets overthe device shown in the FIG. 5, the sheet shows thickness variations of1.15 to 2.4 millimeter. The cap layer thickness varies in an amount ofabout 23 to about 48 micrometers.

Example 3

This example describes the preferred range of LaB₆ in the polycarbonatecore layer when the thickness of the core layer is 1 millimeter.Polycarbonate samples containing various amounts of LaB₆ and 500 ppmIrgaphosl68 were produced on a Werner and Pfleiderer 25 mm twin screwextruder. 1 mm plaques were injection molded on an Engel 75T machine.

The percent of IR radiation that was transmitted was measured on a‘Hitachi U3410 UV-VIS-NIR’. The average of the IR transmission between780 nm-1400 nm was calculated (IR-T %). Irradiation in this wavelengthrange is most responsible for heating. The results are shown in Table 4TABLE 4 Average % LaB6 (IR-T %) 1 mm plaque La B6 g/m² 780-1400 nm LT %Haze 0.0000 0.0000 79 91.1 0.9 0.0016 0.0192 67 87.9 0.78 0.0024 0.028863 86.8 1.07 0.0032 0.0384 56 84.8 1.12 0.0064 0.0768 40 79.1 1.370.0160 0.1920 15 63.2 2.16 0.0320 0.3840 3 40.9 3.37 0.0640 0.7680 021.3 5.29

The data show that no additional IR absorption effect was obtained whenadding more than 0.77% LaB₆ to the polycarbonate core layer, when thethickness of the core layer was 1 millimeter.

From the above examples, it may be seen that it is advantageous to use amultilayered sheet, wherein the core layer contains the IR absorbingadditive. This protects the IR absorbing additive from the effects ofambient moisture thereby increasing the life of the multilayer sheet.Further the results also demonstrate that there exists a synergy tocombining a cap layer containing the UV absorber with a core layercontaining the IR absorbing additive. The results clearly show that inthe aforementioned configuration, there is improved transparency, lowerhaze and better color. These multilayered sheets may thus be effectivelyused in automobiles, residential and office housing.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A multilayered sheet comprising: a core layer comprising athermoplastic polymer and an IR absorbing additive; a first cap layercomprising a thermoplastic polymer and an electromagnetic radiationabsorbing additive; wherein a surface of the first cap layer is disposedupon and in intimate contact with a surface of the core layer.
 2. Thesheet of claim 1, further comprising a second cap layer comprising athermoplastic polymer and an electromagnetic radiation absorbingadditive; wherein the second cap layer is disposed upon and in intimatecontact with a surface of the core layer opposite the surface in contactwith the first cap layer.
 3. The sheet of claim 1, wherein theelectromagnetic radiation absorbing additive is a UV absorber and/or anIR absorbing additive.
 4. The sheet of claim 1, wherein the IR absorbingadditive is lanthanum boride (LaB₆), praseodymium boride (PrB₆),neodymium boride (NdB₆), cerium boride (CeB₆), gadolinium boride (GdB₆),terbium boride (TbB₆), dysprosium boride (DyB₆), holmium boride (HoB₆),yttrium boride (YB₆), samarium boride (SmB₆), europium boride (EuB₆),erbium boride (ErB₆), thulium boride (TmB₆), ytterbium boride (YbB₆),lutetium boride (LuB₆), strontium boride (SrB₆), calcium boride (CaB₆),titanium boride (TiB₂), zirconium boride (ZrB₂), hafhium boride (HfB₂),vanadium boride (VB₂), tantalum boride (TaB₂), chromium borides (CrB andCrB₂), molybdenum borides (MoB₂, Mo₂B₅ and MoB), tungsten boride (W₂B₅),or a combination comprising at least one of the foregoing borides. 5.The sheet of claim 1, wherein the IR absorbing additive comprisesnanosized particles having average particle dimensions of less than orequal to about 200 nanometers.
 6. The sheet of claim 1, wherein the IRabsorbing additive is present in amounts of about 0.001 to about 2.0gram/square meter, measured with respect to the surface of the corelayer.
 7. The sheet of claim 1, wherein the IR absorbing additive ispresent in amounts of about amounts of about 0.02 ppm to about 3000 ppmbased on the total weight of the core layer.
 8. The sheet of claim 7,wherein the core layer comprises thermal stabilizers, and furtherwherein the thermal stabilizers are phosphites, phosphonites,phosphines, hindered amines, hydroxyl amines, phenols, acryloyl modifiedphenols, hydroperoxide decomposers, benzofuranone derivatives, or acombination comprising at least one of the foregoing antioxidants. 9.The sheet of claim 8, wherein thermal stabilizers are present in anamount of about 0.001 to about 3 wt %, based on the total weight of thecore layer.
 10. The sheet of claim 8, wherein the core layer has athickness of about 0.5 to about 30 mm.
 11. The sheet of claim 1, whereinthe thermoplastic polymer is polyacetal, polyacrylic, polycarbonate,polystyrene, polyester, polyamide, polyamideimide, polyarylate,polyarylsulfone, polyethersulfone, polyphenylene sulfide, polyvinylchloride, polysulfone, polyimide, polyetherimide,polytetrafluoroethylene, polyetherketone, polyether etherketone,polyether ketone ketone, polybenzoxazole, polyoxadiazole,polybenzothiazinophenothiazine, polybenzothiazole,polypyrazinoquinoxaline, polypyromellitimide, polyquinoxaline,polybenzimidazole, polyoxindole, polyoxoisoindoline,polydioxoisoindoline, polytriazine, polypyridazine, polypiperazine,polypyridine, polypiperidine, polytriazole, polypyrazole,polypyrrolidine, polycarborane, polyoxabicyclononane, polydibenzofuran,polyphthalide, polyacetal, polyanhydride, polyvinylether, polyvinylthioether, polyvinyl alcohol, polyvinyl ketone, polyvinyl halide,polyvinyl nitrile, polyvinyl ester, polysulfonate, polysulfide,polythioester, polysulfone, polysulfonamide, polyurea, polyphosphazene,polysilazane, or a combination comprising at least one of the foregoingthermoplastic polymers.
 12. The sheet of claim 1, wherein thethermoplastic polymer is bisphenol A polycarbonate,copolyestercarbonate, or a blend of polyester with polycarbonate. 13.The sheet of claim 1, wherein the polyester is a cycloaliphaticpolyester, a polyarylates or a combination of a cycloaliphatic polyesterwith a polyarylate.
 14. The sheet of claim 13, wherein thecycloaliphatic polyester has the structure (X)


15. The sheet of claim 13, wherein the polyarylate is resorcinol arylatepolyesters having the structure (XII)

or the structure (XIII)

where R is a C₁₋₁₂ alkyl or halogen, n is 0 to 3, and m is at leastabout
 8. 16. The sheet of claim 13, wherein the polyarylates are furthercopolymerized to form block copolyestercarbonates, comprising structuralunits of the formula (XVI)

wherein each R¹ is independently halogen or C₁₋₁₂ alkyl, m is at least1, p is about 0 to about 3, each R² is independently a divalent organicradical, and n is at least about
 4. 17. The sheet of claim 1, whereinthe UV absorbers are benzophenones, benzotriazoles, salicylates,resorcinol monobenzoate, 2′ethylhexyl-2-cyano, 3-phenylcinnamate,2-ethyl-hexyl-2-cyano-3,3-diphenyl acrylate, ethyl-2-cyano-3,3-diphenylacrylate, [2-2′-thiobis(4-t-octylphenolate)-1-n-butylamine, orcombinations comprising at least one of the foregoing UV absorbers andwherein the UV absorbers are present in an amount of 5 to about 15 wt %,based on the total weight of the first cap layer.
 18. The sheet of claim2, wherein the UV absorbers are benzophenones, benzotriazoles,salicylates, resorcinol monobenzoate, 2′ethylhexyl-2-cyano,3-phenylcinnamate, 2-ethyl-hexyl-2-cyano-3,3-diphenyl acrylate,ethyl-2-cyano-3,3-diphenyl acrylate,[2-2′-thiobis(4-t-octylphenolate)-1-n-butylamine, or combinationscomprising at least one of the foregoing UV absorbers and wherein the UVabsorbers are present in an amount of 5 to about 15 wt %, based on thetotal weight of the first cap layer.
 19. The sheet of claim 1, having aninfrared absorption of greater than or equal to about 20%.
 20. The sheetof claim 1, having a transmissivity of greater than or equal to about40% in the visible light region.
 21. The sheet of claim 1, having aninfrared absorption of greater than or equal to about 20%, anultraviolet radiation absorption of greater than or equal to about 20%,and a transmissivity of greater than or equal to about 40% in thevisible region.
 22. A method for manufacturing a multilayered sheetcomprising: disposing a first cap layer comprising a thermoplasticpolymer and an ultraviolet radiation absorbing additive onto a surfaceof a core layer comprising a thermoplastic polymer and an IR absorbingadditive.
 23. The method of claim 22, wherein the core layer is producedsimultaneously or sequentially with the first cap layer.
 24. The methodof claim 22, further comprising disposing a second cap layer comprisinga thermoplastic polymer and an ultraviolet radiation absorbing additiveonto a surface of the core layer opposite the surface contacting thefirst cap layer.
 25. The method of claim 24, wherein the second caplayer is produced simultaneously or sequentially with the first caplayer and/or the core layer.
 26. The method of claim 22, wherein thedisposing is conducted in a two roll mill or a three roll mill.
 27. Themethod of claim 22 further comprising thermoforming, vacuum molding,blow molding, injection molding, and/or compression molding themultilayered sheet.
 28. A method for manufacturing a multilayered sheetcomprising: co-extruding a core layer comprising a thermoplastic polymerand an IR absorbing additive with a first cap layer comprising athermoplastic polymer and an ultraviolet radiation absorber.
 29. Themethod of claim 28, further comprising co-extruding a second cap layerwith the first cap layer and the core layer.
 30. The method of claim 28,further comprising laminating the multilayered sheet.
 31. An articlecomprising the sheet of claim
 1. 32. An article comprising the sheet ofclaim
 2. 33. An article made by the method of claim
 22. 34. An articlemade by the method of claim 28.